Hormone Test

Thyroid function test

Dr. Nithin Jayan
Medically Reviewed by Dr. Nithin Jayan, MBBS, DNB
Last Updated on May 23, 2014
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Test : Thyroid function test

Indications : Thyroid hormone tests are done for the following reasons:

• To rule out hypothyroidism in newborns and adults
• To rule out hyperthyroidism
• To assess treatment for hypo / hyperthyroidism

A sample of blood is drawn through venipuncture, transferred to a sterile container and taken to the laboratory. The procedure must be done on an empty stomach. Ask your doctor if you must stop taking your thyroid medications prior to the test. Certain other medications too affect the test results including blood thinners, steroids and anti-seizures medications.

Physiology : Thyroid hormone tests are blood tests that are done to assess the functioning of the thyroid gland.

The thyroid is a butterfly-shaped gland that is located in front of the windpipe, just below the voice box.With the help of iodine absorbed from food it makes two hormones – thyroxin (T4) and tri iodothyronine (T3), which are stored in the thyroid and released according to the body’s need.

Thyroid hormones, T3 and T4 are required for the proper functioning of the brain. During the first few years of life inadequate amounts of thyroid hormones cause intellectual disability. In adults, hypothyroidism, a condition producing low thyroxin levels, affects metabolism and energy absorption.

Normal Range : T4-60-140nmol/L, T3-1.2-1.8nmol/L, TSH-0.1-6IU/L

Interpretation :
Thyroid hormone tests - Normal Values
Total thyroxine (T4): 11.8–22.6 (mcg/dL) in newborns

6.4–13.3 mcg/dL in babies and older children

5.4–11.5 mcg/dL (57–148 nmol/L) in adults

Free thyroxine (FT4): 0.7–2.0 ng/dL nanograms per deciliter (ng/dL)
Total triiodothyronine (T3): 105–245 ng/dL in children of age 1–14

82–213 ng/dL in adolescents ages 12–23

80–200 ng/dL in adults

Free triiodothyronine (FT3): 260–480 picograms per deciliter (pg/dL) or 4.0–7.4 pmol/L in adults
Free thyroxine index (FTI): 1.5-4.5 (index) in adults

Higher than normal values could indicate the following:

• Grave’s disease
• Thyroiditis
• Goiter
• Over consumption of thyroid medications

Lower than normal values could indicate the following:

• Thyroid disease - Thyroiditis
• Pituitary gland disease
• Thyroid gland damage through radiation / surgery

References :

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Suj113, India

i have thyroid problem because of which i have gained weight i.e. obese, i am taking thyronorm 150 mcg...I have many problems as i said earlier i am obese, i am not having my menstruation properly...how to decrease weight and get back my periods...i have shown atleast to four to five doctors (gynecologist as well as endocrinologist) but all of them think me an experiment material and just give medicines and tell all will be normal....no one has cured my problems....only mint money and test on me...please help

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